The invention is directed to a method for recognition of the respective power stroke of the cylinders of a fourstroke engine the four strokes of such an engine being designated as intake stroke, compression stroke, combustion stroke and exhaust stroke.
In electronic control processes employed in such engines, it is important for various signals to recognize the power stroke of every cylinder with precision. For example, in electronic ignition with individual sparking coils, it must be accurately known when a piston is located at a predetermined crank angle differential prior to the top dead center of the combustion stroke.
Two methods are, known in particular for cylinder recognition. One method makes use of the signals of an ignition distributor. An inductive sensor is arranged at an ignition cable, which inductive sensor delivers a signal at every 720.degree. crank angle, since an ignition signal is supplied to the respective cylinder at all 720.degree. crank angles. The power stroke of the monitored cylinder is exactly associated with the occurrence of this sensor signal. If the power stroke of this one cylinder is known, the respective power strokes in which the other cylinders are located is also determinable.
The other method, which is known e.g. from EP 0 058 562, makes use of signals of a camshaft sensor. The camshaft rotates only once during two revolutions of the crankshaft, so that a sensor signal is sent after every 720.degree. revolution of the crankshaft. The power strokes of the individual cylinders are substantially associated with the occurrence of this sensor signal based on the engine construction.
In automobile electronics, it is desirable, in principle, to obtain a desired amount of information with as few sensors as possible. Accordingly, efforts have been made for a long time to develop power stroke recognition in four-stroke engines in such a way that no special sensors are required such as the aforementioned inductive sensor at an ignition cable or the camshaft sensor.
A method for the recognition of the power stroke of a cylinder of an internal combustion engine is known from WO 87/05 971, in which method a quantity modulated in the power stroke, e.g. rate of rotation or pressure in the combustion chamber, is related to the signal of a crankshaft sensor which generates one reference pulse per revolution. The occurrence of a reference pulse and a maximum of the modulated signal enables an unequivocal recognition of the power stroke in an internal combustion engine with an uneven number of cylinders.
However, the known method has the disadvantage that it cannot be used with an internal combustion engine having even number of cylinders.